Japanese Patent Application Publication No. 2009-180987, as an conventional example, discloses a process unit is provided with a photosensitive unit having a photosensitive drum, a developing unit having a developing roller for supplying toner to the photosensitive drum, and a coil spring urging the developing unit so as to permit the developing roller to be in pressure contact with the photosensitive drum.
More specifically, the photosensitive unit has a box shaped casing having an upper opening, and the photosensitive drum is provided at one end of the casing, and the coil spring is provided at another end of the casing. Upon assembly of the developing unit with the photosensitive unit, the developing roller is urged by the coil spring with a predetermined force and is brought to pressure contact with the photosensitive drum.
In another conventional example, a process unit is provided with a pressing member configured to press a developing unit including a developing roller toward a photosensitive drum, and a separating member configured to separate the developing roller from the photosensitive drum against a pressing force of the pressing member. In this process unit, the developing roller is in pressure contact with the photosensitive drum with a predetermined nipping pressure due to the pressing force of the pressing member, and the developing unit is held between the photosensitive drum and the pressing member.